What Is FB2 and Why Convert?
FB2 (FictionBook 2) is an XML-based ebook format that originated in Russia and became the dominant ebook format across Russian-speaking countries. If you have ever downloaded ebooks from Russian digital libraries like Flibusta, Lib.rus.ec, or Litres, you have almost certainly encountered FB2 files.
The format was designed with a specific philosophy: separate content from presentation entirely. Unlike EPUB, which packages HTML and CSS together, FB2 stores the text in a structured XML document with semantic markup for chapters, footnotes, epigraphs, poems, and citations. The reading application then decides how to render the content. This design made FB2 exceptionally clean and portable -- but it also means the format lacks the visual richness of modern ebook standards.
The problem is compatibility. While FB2 readers are common on Android (via apps like FBReader, Moon+ Reader, and CoolReader) and on desktop (via Calibre), the format is essentially unsupported on Kindle, Apple Books, Kobo, Nook, and most Western e-readers and reading platforms. If you want to read your FB2 library on anything other than a dedicated FB2 reader, conversion to EPUB is the practical solution.
FB2 Format Structure
Understanding how FB2 files are structured helps explain what happens during conversion and what to watch for in the output.
An FB2 file is a single XML document with these key sections:
| Section | Purpose | EPUB Equivalent |
|---|---|---|
| description | Metadata (title, author, genre, annotation) | OPF metadata |
| body | Main text content with sections | XHTML content files |
| body (notes) | Footnotes and endnotes | Footnote XHTML files |
| binary | Base64-encoded images | Image files in ZIP |
| stylesheet | Optional CSS (rarely used) | CSS stylesheet |
The FB2 XML schema supports rich semantic markup that maps well to EPUB's HTML structure:
<section>elements become chapters<title>elements become headings<epigraph>elements become styled quotation blocks<poem>and<stanza>elements preserve verse formatting<cite>elements maintain citation structure<footnote>elements with internal links become proper EPUB footnotes
This semantic richness means FB2-to-EPUB conversion can produce high-quality output -- the structural information needed for a good EPUB is already present in the FB2 file.
Method 1: Using Calibre
Calibre is the most reliable tool for FB2 to EPUB conversion, with extensive support for the FB2 format's features.
Basic Conversion
- Install Calibre from calibre-ebook.com (free, open-source, available for Windows, macOS, and Linux)
- Add your FB2 file by dragging it into the Calibre library window
- Select the book in your library list
- Click "Convert books" in the toolbar (or press C)
- Set the output format to EPUB (top-right dropdown)
- Click OK to convert with default settings
The converted EPUB appears in your Calibre library. Right-click and select "Open containing folder" to find the file.
Optimizing for Cyrillic Text
FB2 files with Cyrillic text require attention to font embedding to ensure proper rendering on all devices:
In the Look & Feel tab:
- Enable "Embed font family" and select a font with full Cyrillic coverage (Noto Serif, Liberation Serif, or PT Serif are excellent choices)
- Set the input character encoding to UTF-8 (FB2 files should already be UTF-8, but verifying prevents garbled text)
In the EPUB Output tab:
- Choose EPUB 3 as the output profile for better language support
- Enable "Preserve cover aspect ratio" to maintain the original cover proportions
Pro Tip: If you are converting a large FB2 library with mixed Cyrillic and Latin text, create a Calibre conversion preset with Noto Serif as the embedded font. Noto covers virtually every writing system, so your converted EPUBs will render correctly regardless of language mixing within the text.
Batch Conversion
For large FB2 libraries:
- Add all FB2 files to Calibre
- Select all (Ctrl+A or Cmd+A)
- Click "Convert books" -- Calibre detects the bulk selection
- Configure settings once (they apply to all selected books)
- Click OK and monitor progress in the Jobs indicator
For command-line batch processing:
# Convert a single FB2 to EPUB
ebook-convert input.fb2 output.epub
# With Cyrillic font embedding
ebook-convert input.fb2 output.epub \
--embed-font-family "Noto Serif" \
--output-profile generic_eink
# Batch convert all FB2 files in a directory
for fb2 in *.fb2; do
ebook-convert "$fb2" "${fb2%.fb2}.epub" \
--embed-font-family "Noto Serif"
done
For more on batch processing workflows, see our batch processing files guide.
Method 2: Online Conversion Tools
The ebook converter on ConvertIntoMP4 supports FB2 to EPUB conversion directly in your browser. Upload the FB2 file, select EPUB as the output format, and download the result. This method is convenient for quick, one-off conversions without installing software.
For users who need to convert FB2 files to other formats, the document converter supports additional output options including PDF, which is useful when you need to share a book with someone who does not have an e-reader. See our guide on how to convert EPUB to PDF for details on that workflow.
Method 3: FBReader
FBReader, the popular reading app originally designed for FB2 files, can export to EPUB on some platforms:
- Open the FB2 file in FBReader
- Use the export or share function (availability varies by platform)
- Select EPUB as the export format
FBReader's export is basic compared to Calibre -- it handles simple text conversion well but may not preserve complex formatting, footnote links, or metadata as thoroughly.
Method 4: fb2epub Command-Line Tool
For developers and power users, the fb2epub tool provides direct conversion:
# Install via pip
pip install fb2epub
# Basic conversion
fb2epub input.fb2 output.epub
# The tool handles Cyrillic text natively
This tool focuses specifically on the FB2-to-EPUB conversion path and handles the format's quirks well, including proper footnote linking and image extraction.
Preserving Metadata During Conversion
FB2's metadata structure is rich but uses different conventions than EPUB. Here is how the metadata maps:
| FB2 Metadata Field | EPUB Equivalent | Conversion Notes |
|---|---|---|
| book-title | dc:title | Transfers directly |
| author (first-name, last-name) | dc:creator | Names may need reordering (Russian convention is last-first) |
| genre | dc:subject | FB2 uses specific genre codes; may need human-readable labels |
| annotation | dc:description | HTML annotation content is flattened to text |
| lang | dc:language | Transfers directly (usually "ru" for Russian) |
| sequence (name, number) | calibre:series | Calibre preserves series info; standard EPUB lacks series metadata |
| coverpage image | Cover image | Extracted from base64 binary data |
| date | dc:date | May be publication date or file creation date |
Common Metadata Issues
Author name order: Russian FB2 files often store author names in the Russian convention (family name first). Calibre can reformat to Western order (given name first) in the metadata editor.
Genre codes: FB2 uses a closed set of genre codes like sf_fantasy, det_crime, prose_classic. These do not map directly to standard subject headings. Calibre converts them to human-readable labels, but you may want to edit them manually for clarity.
Series information: FB2 has native support for book series with sequence numbers. Calibre preserves this information in its own metadata format. Standard EPUB does not have a series field, but most reading apps that support Calibre's metadata extensions will display series information correctly.
Pro Tip: Before batch converting a large FB2 library, convert one or two representative files first and check the output thoroughly on your target e-reader. Verify that Cyrillic text renders correctly, footnote links work, images display properly, and the table of contents is structured correctly. Fixing a systematic issue before batch processing saves considerable time.
Handling Common Conversion Issues
Garbled Cyrillic Text
If the converted EPUB shows garbled characters instead of Cyrillic text:
- Check the FB2 file's encoding declaration (should be UTF-8)
- In Calibre, set the input encoding explicitly to UTF-8 in the conversion dialog
- If the file uses Windows-1251 encoding (common in older Russian ebooks), set the input encoding to CP1251
Missing or Broken Footnotes
FB2's footnote system uses internal links between the main text and a separate notes body section. During conversion:
- Calibre usually handles these correctly, converting them to EPUB footnote links
- If footnotes appear as dead links, check that the FB2 file's footnote
idattributes match the link references - Some FB2 files use non-standard footnote markup that converters may not recognize
Image Quality Issues
FB2 stores images as base64-encoded data within the XML file. During conversion:
- Images are extracted and stored as separate files in the EPUB
- Quality is preserved (no re-encoding occurs)
- If images appear missing, the FB2 file may reference images by incorrect IDs
- Very large images (common in illustrated books) convert correctly but may increase the EPUB file size
Table of Contents Problems
FB2's section structure should produce a clean EPUB table of contents, but issues arise when:
- The FB2 file uses non-standard section nesting
- Chapter titles are missing or empty
- The file uses flat structure instead of nested sections
In Calibre, use the "Table of Contents" tab in the conversion dialog to configure how chapter detection works. Setting the TOC detection to "Use headings" or adjusting the XPath expressions can fix structural issues.
Why Convert to EPUB Instead of Other Formats?
If you are leaving the FB2 ecosystem, EPUB is the best target format for several reasons:
Universal compatibility. EPUB works on Kobo, Nook, Apple Books, Google Play Books, and dozens of reading apps. Even Kindle now supports EPUB via Send to Kindle.
Feature parity. EPUB 3 supports everything FB2 can represent and more: embedded fonts, multimedia, interactive content, and accessibility features.
Open standard. Like FB2, EPUB is an open format. Your converted library is not locked into any single vendor's ecosystem.
Active development. EPUB continues to receive updates and improvements. FB2 development has been largely dormant for years, with no major specification updates.
If you need Kindle-specific output, convert to EPUB first and then to AZW3 or MOBI. Our EPUB to PDF converter and PDF to EPUB converter are also useful for moving between ebook and document formats. For a comparison of Kindle formats, see our AZW3 vs EPUB vs MOBI comparison. For a broader overview of ebook formats, check our best ebook format guide.
FB2 Features That Convert Well (and Those That Do Not)
Converts well:
- Chapter structure and navigation
- Footnotes and endnotes with working links
- Basic text formatting (bold, italic, headings)
- Cover images
- Epigraphs and citations
- Poetry and verse formatting
- Metadata (title, author, language)
May need attention:
- Complex table layouts (FB2's table support is basic)
- Inline images referenced by non-standard IDs
- Custom stylesheet rules (rarely used in FB2 but occasionally present)
- Annotation HTML with embedded formatting
Does not convert:
- FB2-specific rendering instructions (these are reader-dependent anyway)
- Some genre-specific markup extensions used by individual FB2 libraries
Building a Conversion Workflow for Large Libraries
If you have hundreds or thousands of FB2 files to convert, here is an efficient workflow:
- Organize your FB2 files by author or series in a directory structure
- Import into Calibre (Calibre handles thousands of books efficiently)
- Review and fix metadata using Calibre's bulk metadata editor
- Create a conversion preset with your preferred settings (output format, font embedding, output profile)
- Batch convert using the preset
- Spot-check results on your target e-reader
- Export the EPUB files to your e-reader or cloud library
For automation beyond what Calibre's GUI offers, the command-line ebook-convert tool can be scripted with shell scripts or integrated into larger workflows. See our guide on how to automate file conversions for more on building automated pipelines.
The ebook converter can also handle FB2 conversions online if you prefer not to install software, and the document converter provides additional format options beyond ebook-specific outputs.
Wrapping Up
FB2 to EPUB conversion is a well-trodden path with reliable tools and predictable results. The structural similarity between FB2's XML-based content model and EPUB's HTML-based content model means that conversion preserves the vast majority of formatting and metadata.
Calibre remains the best tool for the job, especially for large libraries and for files requiring Cyrillic font embedding. Online converters provide a convenient alternative for occasional conversions. Whichever method you choose, the result is an EPUB file that works across virtually every modern reading platform -- a significant upgrade from FB2's limited device support.
